Accessing FormBuilderState currentState value within dispose

[judsonjames]

I'm using Flutter Form Builder in order to collect data, then save to my database using Isar. When a user pops the widget either with the OS dependent "back button" or the "back button" on the AppBar, I want to store the state of the Form to a draft value. However, also I'm utilizing GoRouter, which doesn't work with WillPopScope. It works fine on my desktop emulator, but on a native Android device it will fail to pop the widget with either back button. So, given a Widget that looks like this:

class _MyWidgetState extends State<MyWidget> {
  final _formKey = GlobalKey<FormBuilderState>();
  late Isar _isar;

  @override
  void initState() {
    super.initState();
    _isar = context.read<IsarModel>().isar;
  }
  
  // I know this doesn't work, but this is ideally what I'd like to use
  @override
  void dispose() {
    if (_formKey.currentState?.value != null) {
      // write values from Form to Isar entry
    }
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FormBuilder(
        key: _formKey,
        body: Column(
          // FormBuilderFields
        )
      );
  }
}

I can't get the form value because the widget has already popped from the tree and doesn't exist. I can't use the willPopScope property of FormBuilder because it conflicts with GoRouter. I've tried using routerDelegate to get the data, but it gives inconsistent results from FormState depending on what fields were populated.

I've considered using Provider to cache the data of the Form from the onChanged callback on FormBuilder but I think that's overkill and could be a performance hit. Are there any other alternatives native to FlutterFormBuilder that allow the FormState to be accessed before the widget is popped?

[deandreamatias]

Hi, sorry for delay response
Maybe you can use onChange property of FormBuilder to save values when changes.
Remember to use _formKey.currentState?.instantValue instead _formKey.currentState?.value, like I explain here.
Also, the getters _formKey.currentState?.isDirty and _formKey.currentState?.isTouched can be useful